Postharvest changes in the phenolic profile of watercress induced by post-packaging irradiation and modified atmosphere packaging

Impact of Processing Approach and Storage Time on Bioactive and Biological Properties of Rocket, Spinach and Watercress Byproducts

The high nutritional value of vegetables is well recognized, but their short shelf life and seasonal nature result in massive losses and wastes. Vegetable's byproducts are an opportunity to develop value-added ingredients, increasing food system efficiency and environmental sustainability. In the present work, pulps and powders of byproducts from rocket and spinach leaves and watercress were developed and stored for six months under freezing and vacuum conditions, respectively. After processing and storage, microbiological quality, bioactive compounds (polyphenols, carotenoids and tocopherols profiles), antioxidant capacity, and pulps viscosity were analyzed. Generally, the developed vegetable's pulps and powders were considered microbiologically safe. Although some variations after processing and storage were verified, the antioxidant activity was preserved or improved. A rich phenolic composition was also registered and maintained. During freezing, the quantitative carotenoid profile was significantly improved (mainly in rocket and spinach), while after drying, there was a significant decrease. A positive effect was verified in the vitamin E level. Both processing and storage conditions resulted in products with relevant phenolics, carotenoids and tocopherol levels, contributing to the antioxidant activity registered. Thus, this study demonstrates the potential of vegetable byproducts valorization through developing these functional ingredients bringing economic and environmental value into the food chain.

In through the out door: Biochemical mechanisms affecting flavonoid glycoside catabolism in plants

Plants are the sole source of flavonoids, a chemical category that includes flavonols. For the most part, flavonols occur as glycosides with numerous postulated biological roles in plants, including photoprotection, modulation of hormone translocation, and sequestration of reactive oxygen species. Flavonol glycosides are often considered as dead-end metabolites because related flavonoids (i.e., anthocyanins) occur in terminal tissues such as flowers and fruit, but recent evidence points to their turnover in planta, including developing photosynthetic tissues. Although microbial degradation pathways for flavonol glycosides of plant origin are well described, plant catabolic pathways are little studied by comparison. This review will address our current understanding of biochemical processes leading to the loss of flavonol glycosides in plants, with a specific emphasis on the evidence for flavonol-specific β-glucosidases. Complete elucidation of these catabolic pathways is dependent on the identification of regiospecific modifying steps, including enzymes associated with the hydrolysis of rhamnosylated flavonols, as well as flavonol peroxidation and their encoding genes. Herein, we highlight challenges for the identification of hypothetical plant α-rhamnosidases and peroxidases involved in flavonol glycoside degradation, and the potential biological role of this catabolism in mitigating oxidative stress in developing and postharvest plant tissues.

Valorisation of the green waste parts from turnip, radish and wild cardoon: Nutritional value, phenolic profile and bioactivity evaluation

The recovery of bio-wastes to obtain high added value compounds is of great interest for the pharmaceutical, medicinal and food industries. Therefore, the aerial parts of turnip (Brassica rapa L.), radish (Raphanus sativus L.) and leaf blade of wild cardoon (Cynara cardunculus L. var. sylvestris (Lamk) Fiori) were characterized regarding their nutritional composition, as also their content in soluble sugars, organic acids, fatty acids, and tocopherols. Furthermore, their hydroethanolic extracts and infusion preparations, were profiled regarding individual phenolic compounds by HPLC-DAD/ESI-MS and their antioxidant, antibacterial and hepatotoxic activities were evaluated. Regarding the nutritional content, wild cardoon revealed the best results, however it was radish and turnip that showed higher values for organic acids and phenolic compounds. The hydroethanolic extract and infusion preparation of wild cardoon stood out for its antioxidant and antibacterial activity. Overall, the hydroethanolic extracts seemed more effective (regarding antioxidant and antibacterial activity) than the infusions. Total phenolic acids proved to be strongly correlated with the antioxidant and antibacterial (against Morganella morganii) activities. This study showed that the discarded parts of these plants can be used as an important natural source of valuable nutrient content and new and safe bioactive compounds, beneficial for human health. Moreover, the extraction of those compounds from underused parts of turnip, radish and cardoon could be used to preserve foods, avoiding artificial additives and thus, contributing to the development of new natural ingredients.